Challenging a common perception that personality traits are ingrained, researchers have found that when preschoolers spend time around one another, they tend to take on each others' personalities.

The study, published online in the Journal of Personality and Social Psychology, suggests personality is shaped by environment and not just genes.

"Our finding, that personality traits are 'contagious' among children, flies in the face of common assumptions that personality is ingrained and can't be changed," said co-investigator on the study Jennifer Watling Neal, Associate Professor at Michigan State University in the US.

"This is important because some personality traits can help children succeed in life, while others can hold them back," she explained.

For the study, the researchers studied two preschool classes for an entire school year, analyzing personality traits and social networks for one class of three-year-olds and one class of four-year-olds.

Children whose play partners were extroverted or hard-working became similar to these peers over time.

Children whose play partners were over-anxious and easily frustrated, however, did not take on these particular traits, the study said.